Status and recent development of the nitrogen cryogenic system for the NICA accelerator complex at JINR.

The new NICA (Nuclotron-based Ion Collider fAcility) accelerator complex is scheduled to be put into operation in 2019 at JINR in Dubna. This facility comprising the existing Nuclotron together with two newly created superconducting accelerators – booster and collider – will require additional refrigeration capacity at 4.5 K and 77 K. The helium cryogenic system of the NICA complex will be created as a result of the modernization of the existing equipment for cryogenic supply of the Nuclotron, but the liquid nitrogen plant will be completely new. It will be based on a 1300 kg/h nitrogen liquefier and two 500 kg/h re-condensers of nitrogen vapor. This report describes the schematic diagram of the system of liquid nitrogen that will be used for shield refrigerating at 77 K and at the first stage of cooling down three accelerator rings with the total length of about 1 km and the “cold” mass of 290 tons. We demonstrate the status and recent development of the nitrogen cryogenic system: location, basic parameters and design of major components and discuss their phased commissioning.

新型NICA（Nuclotron-based Ion Collider fAcility）加速器综合体计划于2019年在杜布纳的JINR投入运行。该综合体包含现有Nuclotron加速器与两台新建超导加速器——增强器与对撞机，将需要4.5K和77K温区的额外制冷容量。NICA综合体的氦制冷系统将通过改造现有Nuclotron低温供应用设备实现，但液氮装置将为全新搭建。该液氮系统将依托一台1300 kg/h的氮气液化器与两台500 kg/h的氮气蒸汽再冷凝器。本报告阐述了该液氮系统的原理图，该系统将用于77K温区的屏蔽制冷，以及三台总长度约1km、“冷质量”达290吨的加速器环的初期冷却阶段。本文展示了该氮制冷系统的现状与最新进展，包括其布局、核心组件的基本参数与设计方案，并讨论了其分阶段调试工作。